Amylose and β‐Glucan Content of New Waxy Barleys

Starch was isolated from four new waxy barleys and compared with normal and high‐amylose barley starch. The waxy barley samples were selected lines from crosses of Swedish hulled and naked barley cultivars with the cultivar Azhul as donor of the waxy gene. The starches from the waxy barley samples were found to contain 0.7–2.6% amylose when determined iodimetrically by amperometric titration and 0.0–0.9% when determined by size exclusion chromatography after debranching. However, Sepharose CL‐2B elution profiles of the starches detected by iodine staining showed that all four waxy samples were free from detectable amounts of amylose. The amylopectin starches were found to contain a small polysaccharide fraction with molecular size smaller than amylopectin, with an iodine staining λ_max range of 550–600 nm. The water extractable and acid extractable β‐glucan contents in the waxy barley cultivars were generally found to be higher than those in normal barley.     

Bestimmung der Molekulargewichtsverteilung in nativen Stärken durch Gelchromatographie

Determination of the Distribution of Molecular Weights in Native Starches by Gel Chromatography . The distribution of the molecular weights of polysaccharides in corn, potatoe and rice starch were investigated by fractionation of starch polysaccharides in a gel chromatographic system. The amylopectin component of the dispersed starch was excluded from the gel. Therefore the conclusion is likely that the molecular weight of amylopectin is higher than 20 × 10⁶. The gel columns were calibrated by chromatography of dextran fractions of known molecular weight. By comparison of the elution volumes of dextran fractions of know molecular weight with the elution volumes of amylose fractions it was possible to determine their molecular weights. From curves of molecular distribution the amount of amylose as percentage of total amylose can be determined. The average molecular weight of potatoe amylose (M̄_w 50%) is about 400 000 whereas it amounts to 100 000–200 000 in the case of rice and corn starch. The amylose of a “High Amylose Starch” (about 75% amylose) has a molecular weight of 50 000.     

Die Bindung flüchtiger Aromastoffe an Stärke

The Binding of volatile Aroma Compounds by Starch. The sorption of volatile aliphatic alcohols, aldehydes, ketones, esters, amines, of some aromatic and heteroaromatic compounds by starch, amylose, amylopectin, dextrin and glucose was investigated with gravimetric, IR- and UV-spectrophotometric methods. Dry starch swells with ethanol and n-butylamin to a great extent, with ethyl acetate to a very small one, with n-hexane not at all. Humid starch sorbs greater amounts of aroma compounds, depending of the water content. The most aroma compounds may be bound by hydrogen bonds. Inclusion is found by drying under suitable conditions. The sorbed amounts by amylose and amylopectin do not differ very much. A very tight binding is observed after mixing aroma compounds with amylose, not with amylopectin. Dextrin and especially glucose are sorbing smaller amounts than starch in water containing systems.     

Characterization of Physical Properties of Flour and Starch Obtained from Gamma‐Irradiated White Rice

Physical and structural characteristics of rice flour and starch obtained from gamma‐irradiated white rice were determined. Pasting viscosities of the rice flour and starch, analyzed by using a Rapid Visco Analyser, decreased continuously with the increase in irradiation dosage. Differential scanning calorimetry showed that gelatinization onset, peak and conclusion temperatures of rice flour and starch changed slightly but the enthalpy change decreased significantly with increase of irradiation dosage. All irradiated starch displayed an A‐type X‐ray diffraction pattern like the native starch. Gel permeation chromatography showed that the blue value ratio of the first peak (amylopectin) to the second one (amylose) decreased with the increase of the irradiation dosage. The weight‐average molecular weight (M_w) and gyration radius (R_z) of amylopectin analyzed by using HPSEC‐MALLS‐RI (high‐performance size‐exclusion chromatography equipped with multiangle laser‐light scattering and refractive index detector) decreased gradually from 1.48×10⁹ (M_w) and 384.1 nm (R_z) of native rice starch to 2.36×10⁸ (M_w) and 236.8 nm of 9 kGy‐irradiated starch. The branch chain‐length distribution of amylopectins determined by HPAEC‐ENZ‐PAD (high‐performance anion‐exchange chromatography with amyloglucosidase post‐column on‐line reactor and pulsed amperometric detector) showed that gamma irradiation had no significant effect on the amylopectin branch chains with 13≤DP≤24 and 37≤DP, but produced more branch chains with 6≤DP≤12 when the irradiation dosage was less than 9 kGy. It might be deduced that gamma irradiation caused the breakage of the amylopectin chains at the amorphous regions, but had little effects on the crystalline regions of starch granules, especially at low dosage irradiation.     

Chain‐length Distribution Profiles of Amylopectin Isolated from Endosperm Starch of Waxy and Low‐amylose Bread Wheat (Triticum aestivum L.) Lines with Common Genetic Background

Large A‐type endosperm starch granules were isolated from near‐isogenic waxy and non‐waxy lines and low‐amylose mutant lines of bread wheat with a common genetic background. The amylose contents of A‐type starch ranged from 2.6% to 23.6%. Amylopectin was isolated by concanavalin A (Con A) precipitation from the isolated starch. The λ_max (range: 532‐538 nm) and blue values at 680 nm (range: 0.026‐0.037) of the iodine‐amylopectin complex were not significantly different among the isolated amylopectins, indicating that amylopectins from non‐waxy and low‐amylose lines did not contain such long chains as amylose or extra‐long chains of amylopectin affecting iodine complex properties. Chain‐length distribution profiles measured by both high‐performance size‐exclusion chromatography (HPSEC) and high‐performance anion‐exchange chromatography (HPAEC) showed that the amylopectin structures of these lines were indistinguishable from each other. Extra‐long chains were not detected in the amylopectins by HPSEC measurement. The side‐chains measured by HPAEC were classified into four groups according to their degree of polymerization (DP), and the proportion of each group were in the following ranges: DP 6‐12, 26.5‐27.5%; DP 13‐24, 43.6‐44.1%; DP 25‐36, 13.6‐14.2%, and DP 37‐60, 11.0‐11.7%. The alleles on the Wx‐D1 locus, i.e., Wx‐D1a, Wx‐D1d, Wx‐D1f, and Wx‐D1g, responsible for granule‐bound starch synthase (GBSS I) biosynthesis had no influence on the properties of iodine‐amylopectin complex and the chain‐length distribution profiles of amylopectin.     

A Study of the Internal Structure in Cassava and Rice Amylopectin

Cassava and rice amylopectins and their ϕ,β‐limit dextrins were debranched and the unit chain compositions were analyzed by gel permeation chromatography and high performance anion‐exchange chromatography. The content of amylose and super‐long amylopectin chains was 15.5‐15.6% and 0.8‐1.2% in cassava and 15.1‐18.7% and 3.4‐8.6% in rice starches, respectively. The internal unit chain profiles of the amylopectin samples were obtained from the ϕ,β‐limit dextrins. Short B‐chains were subdivided into a major group (BS_major) with a degree of polymerization (DP) of 8‐25 and a minor group of “fingerprint” B‐chains (B_fp) with DP 3‐7. Cassava and rice amylopectins possessed different amounts and patterns of B_fp‐chains. The rice samples contained higher amounts of B_fp‐chains, which suggested larger size of its clusters when compared with cassava. The content of the shortest “fingerprint” A‐chains (A_fp) was also variable, especially between the rice cultivars. The position of the internal chains in the original amylopectin chain profile was traced. The reconstructed B‐chain profiles fitted well with the original profiles. This implied that most of the B‐chains carried external chain segments of similar lengths, which corresponded to the experimentally measured average length.     

Das Verhalten der beiden chromatographisch trennbaren Amyloseanteile bei der oxydativen Behandlung von Kartoffelstärke

The Behaviour of the two Separable Amylose Components during Oxidative Treatment of Potato Starch. During oxidative degradation of potato starch by means of sodium persulphate changes in both column and paper chromatography of the components amylose and amylopectin were proved. The fact that in the paper chromatogram one amylose component is degraded to a higher dextrine with a second amylose component as intermediate product has been proved.     

Analysis of Starch in Food Systems by High‐Performance Size Exclusion Chromatography

Starch has unique physicochemical characteristics among food carbohydrates. Starch contributes to the physicochemical attributes of food products made from roots, legumes, cereals, and fruits. It occurs naturally as distinct particles, called granules. Most starch granules are a mixture of 2 sugar polymers: a highly branched polysaccharide named amylopectin and a basically linear polysaccharide named amylose. The starch contained in food products undergoes changes during processing, which causes changes in the starch molecular weight and amylose to amylopectin ratio. The objective of this study was to develop a new, simple, 1‐step, and accurate method for simultaneous determination of amylose and amylopectin ratio as well as weight‐averaged molecular weights of starch in food products. Starch from bread flour, canned peas, corn flake cereal, snack crackers, canned kidney beans, pasta, potato chips, and white bread was extracted by dissolving in KOH, urea, and precipitation with ethanol. Starch samples were solubilized and analyzed on a high‐performance size exclusion chromatography (HPSEC) system. To verify the identity of the peaks, fractions were collected and soluble starch and beta‐glucan assays were performed additional to gas chromatography analysis. We found that all the fractions contain only glucose and soluble starch assay is correlated to the HPSEC fractionation. This new method can be used to determine amylose amylopectin ratio and weight‐averaged molecular weight of starch from various food products using as low as 25 mg dry samples.     

Fine Structure of Mung Bean Starch: An Improved Method of Fractionation

Laboratory isolated mung bean starch was fractionated into its amylose and amylopectin components using a modified procedure. The resulting products were shown to be both homogeneous and more susceptible to the hydrolyzing enzymes commonly used for structural analysis. The fine structure of the fractions was investigated using hydrolytic enzymes, chemical analysis and gel filtration chromatography. Differences in amylose/amylopectin fractions isolated by the modified and conventional extraction procedures were apparent. The unit chain length of amylopectin, DP_n and limiting viscosity number of amylose were all lower for samples isolated by the modified method. In contrast the enzymatic hydrolysis of both the amylose and amylopectin fractions was improved for the material extracted by the modified method, low levels of branching and a unit chain distribution by gel filtration chromatography of the two overlapping populations with average degree of polymerization of 42 and 14 was obtained.     

Effects of Wheat Starch Contents on Malt Qualities

The relationships between wheat starch content and wheat malt qualities were studied in the present work. Six wheat varieties that were typical in starch, protein content and amylopectin/amylose ratio were selected from 12 wheat varieties and germinated under the same conditions. The decreased degree of total starch content after malting had a positive correlation (r = 0.8020, P < 0.1) with the amylopectin/amylose ratio of the raw wheat. Extracts of wheat malts were influenced by starch content and the amylopectin/amylose ratio of the raw wheat. When the amylopectin/amylose ratio was in the range 3.65:1?3.93:1, extracts of the malts had significant positive correlation (r = 0.967, P = 0.002) with the starch content of the raw wheat. In this investigation a suitable amylopectin/amylose ratio (3.65:1 to 3.93:1), a high starch content and a low protein content were the characteristics of a wheat variety suitable for malting.     

New Starch Phosphate Carbamides of High Swelling Ability: Synthesis and Characterization

The paper describes the synthesis of starch phosphate carbamides by reacting starch with phosphoric acid and urea. A solid state technique in vacuum at elevated temperatures is used. The degree of substitution of phosphate (DS_P) and carbamide groups (DS_C) can be adjusted by the molar ratio of starch: phosphoric acid: urea, the reaction temperature, and time. The starch derivatives prepared show remarkable swelling if the DS_P ranges between 0.2 and 0.3. With increasing content of urea in the reaction mixture the water‐holding ability is still significantly improved, which is explained by chemically and especially physically introduced urea into the starch polymer. Furthermore, the ratio of amylose: amylopectin of the starch samples influences both the DS values and the physicochemical properties, e.g., swelling power and multivalent metal ion adsorption of the products. The structure of the new polymers was determined by means of FTIR, ¹³C‐ and ³¹P NMR spectroscopy as well as by gel permeation chromatography (GPC).     

The importance of amylose and amylopectin fine structures for starch digestibility in cooked rice grains

Statistically and causally meaningful relationships are established between starch molecular structures (obtained by size-exclusion chromatography, proton NMR and multiple-angle laser light scattering) and digestibility of cooked rice grains (measured by in vitro digestion). Significant correlations are observed between starch digestion rate and molecular structural characteristics, including fine structures of the distributions of branch (chain) lengths in both amylose and amylopectin. The in vitro digestion rate tends to increase with longer amylose branches and smaller ratios of long amylopectin and long amylose branches to short amylopectin branches, although the statistical analyses show that further data are needed to establish this unambiguously. These new relationships between fine starch structural features and digestibility of cooked rice grains are mechanistically reasonable, but suggestive rather than statistically definitive.     

Effects of molecular characteristics of on konjac glucomannan glass transitions of potato amylose, amylopection and their mixtures

BACKGROUND: The purpose of this study was to explore further the functions of konjac glucomannan (KGM) in starch‐based foods. Experiments were carried out using the mixed amylose/amylopectin/KGM system as a model. High‐speed differential scanning calorimetry (hyper‐DSC) with the support of high‐performance size exclusion chromatography (HPSEC) equipped with multi‐angle laser light scattering (MALLS) and differential refractive index (RI), X‐ray diffractometry (XRD) and viscosimetry was used to investigate the effects of KGM on glass transition temperatures (T_gs) of mixtures with different amylose/amylopectin ratios. RESULTS: Hyper‐DSC results showed that the T_gs of amylose, amylopection and their mixtures decreased with increasing concentration of KGM. Based on the molecular characteristics of KGM, HPSEC‐MALLS‐RI, viscosimetry and XRD results showed that the molar masses of KGM ranged from 1.023 × 10⁶ to 1.329 × 10⁶ g mol^?1; the root mean square (RMS) radii were distributed from 110.5 to 129.6 nm, and M_w/M_n was 1.017. KGM was a linear molecule with random‐coil conformation in solution and the crystallinity was 0.00%. CONCLUSION: It is suggested that the addition of KGM has plasticizing effects on the structures of amylose and amylopectin, which can increase free volume and molecular movement of amylose and amylopectin chains, resulting in a decrease in their T_gs. Copyright © 2010 Society of Chemical Industry     

Beeinflussung der Aktivität der Stärkephosphorylase aus Vicia-faba-Kotyledonen durch Lysolecithin

Effect of Lysolecithin on the Activity of Starch Phosphorylase from Vicia faba Cotyledons. The presence of increasing amounts of lysolecithin reduces the activity of phosphorylase I, of V. faba cotyledons, during the synthesis of amylose and amylopectin and during phosphorolysis of amylose. On the other hand, lysolecithin has little effect on the breakdown of amylopectin. Comparisons were made between the synthetic activities of phosphorylase I with increasing amounts of amylopectin or lysolecithin-amylopectin-complex as a primer. The rates were lower with the complex than with amylopectin devoid of lipid. Calculation of transfered glucose residues per non-reducing end group of primer showed that the presence of lysolecithin did not influence the elongation of 6–7 glucose residues per non-reducing end group.     

Fractionation of Starch by Gel Filtration on Agarose Beads

A chromatographical system consisting of a Sephadex G 200 column and an agarose 2B or 4B column was used for fractionation of native starches. Fractionation of the amylose and amylopectin components was achieved, and the amylose part of starch was subfractionated according to its molecular weight. The molecular weight of amylopectin is beyond the fractionation limit of the agarose and seems to be higher than 20 × 10⁶.     

The Influence of Thiocyanate Ions on the Formation of the Starch‐Iodine Complex

The redox reaction between thiocyanate and iodine species present in an aqueous solution of KI results in the formation of thiocyanogen, (SCN)₂. This reaction interferes with the formation of inclusion complexes of a potato amylose with iodine species such as I₃^‐ and I₅^‐. As these ions react with thiocyanate ions (SCN^‐) the blue colour of the amylose‐iodine complex diminishes. The rate of this decrease depends upon the concentration of both the SCN^‐ and the iodine, and appears to follow pseudo‐second order kinetics. Using a UV/visible spectrophotometer the reaction of iodine with KSCN can be followed, with or without amylose, and shows a lowering in concentration of iodine species absorbing at 290–300 nm, together with a lowering in absorbance at 630 nm, due to a lesser amount of the amylose‐iodine complex. Interference with iodine complex formation was also noted with a potato amylopectin. The technique provides the basis for the study of other reactions of iodine such as that with selenocyanate (SeCN^‐).     

银杏淀粉的分离和纯化

用重结晶法可以得到纯度较高的银杏直链淀粉和支链淀粉。凝胶过滤色谱表明：银杏直链淀粉的分子量比玉米直链淀粉的小,而支链淀粉的分子量则具有较宽的分布。银杏直、支链淀粉的碘亲和力分别为19．19％和0．13％,蓝值分别是0．85和0．12,γmax为626nm和564nm;银杏淀粉中直链淀粉含量为33％。     

Starch Biosynthesis. I. The Size Distributions of Amylose and Amylopectin and Their Relationships to the Biosynthesis of Starch

Equations for the size distributions of both linear and branched polymers were applied to debranched amylopectin, linear amylose, and branched amylose polymers. The experimental size distribution of linear amylose corresponds to the broad size distribution of an A–B condensation polymer, whereas that of debranched amylopectin linear chains corresponds to the much narrower Poisson size distribution. These dramatic differences illustrate that different types of enzymes synthesize the linear chains of amylose as compared to those of amylopectin. These results support the previously proposed mechanism. The polymodal behavior of debranched amylopectin is due to the existance of individual Poisson-type polymers created by tier structures in a statistically formed precursor glycogen. Equations were developed which enable the calculation of the percentages of these individual Poisson polymers. When applied to the differences between shx and Bomi barley amylopectins, it is concluded that both studies agree that two different short, inner tier, A-chains exist, where the longer chain is located in the more external third tier in the amylopectins. In amylose, three different polymers exist: A linear amylose A–B type condensation polymer, a branched amylose which behaves as a statistical A–R–B₂ type polymer, and an intermediate, non-statistically branched amylose polymer.     

Enzymatic Characterisation of Novamyl®, a Thermostable α-Amylase

The thermostable -amylase Novamyl^® is used in the baking industry as an antistaling agent due to its ability to reduce retrogradation of amylopectin. We have studied its enzymatic properties at pH 5.0. We make two main conclusions: (1) Novamyl^® shows sequence homology to cycloglycosyl transferases (CGTases); like these enzymes, Novamyl^® cleaves cyclodextrins, forms transglycosylation products and is subject to product inhibition by maltose. Novamyl^® has 5 subsites in the active site and is also subject to substrate inhibition. (2) Novamyl^® is clearly different from exoglucanases like β-amylase and glucoamylase. It is able to hydrolyse a pentasaccharide with bulky substituents at both ends (INdp5) and is inhibited by the α-amylase inhibitor Trestatin A. Although Novamyl^® appears unable to hydrolyse α-1,6-linkages, it is able to degrade amylopectin to a greater extent than β-amylase as well as β-limit dextrins. Novamyl^® degrades amylose in such a manner that initially the molecular weight is drastically reduced while β-amylase does not show any detectable effect on the molecular weight of this substrate. Products of the degradation of amylopectin and amylose by Novamyl^® are maltose and oligosaccharides, whereas β-amylase and glucoamylase produce only maltose and glucose, respectively. This was shown in baking experiments as well. The new data presented here clearly show that unlike exoamylases, Novamyl^® does not require a non-reducing end and attacks amylose, Indp5 and cyclodextrins in an endo-like manner. Based on these results Novamyl^® should be reclassified.     

Amidons Lintnérisés Etudes chromatographique et enzymatique des résidus insolubles provenant de l'hydrolyse chlorhydrique d'amidons de céréales,en particulier de maïs cireux

Lintnerized Starches. Chromatographic and Enzymatic Studies of Insoluble Residues from Acid Hydrolysis of Various Cereal Starches, Particularly Waxy Maize Starch . Native cereal starches, particularly waxy maize starch, have been carefully hydrolyzed at 35°C with hydrochloric acid (2,2-N) in heterogeneous phase. Observation of the course of hydrolysis as a function of time makes it possible to classify the starches according to their acid lability. The kinetic values distinctly reveal two phases, i.e. a fast hydrolysis of the amorphous fraction and a slower degradation of the crystalline starch grain fraction. This observation was confirmed by X-ray diffractometric patterns. The hydrolysis speed of acid resistant fractions seems to become slower as the apparent amylose ratio increases. The change in the macromolecular structure of the obtained granular residues or “lintnerized” starches as a function of time was examined after aqueous solubilization by means of gel chromatography using a calibrated Sephadex G-50 column. Lintnerization causes a decrease in the apparent DP of the chains of the starch residues and two subgroups with apparent DP 13 and 25 appear rapidly. These DP are unchanging with time of acid treatment. The chromatographic and enzymatic studies of lintnerized starches were performed directly and after successive enzymatic digests with pullulanase and ß-amylase. After debranching of solubilized residues with pullulanase and gel chromatography a linear chain subgroup of DP 15–20 appears. This one is in fact composed of two subgroups: one more important with a DP 13, the other broad distribution with a DP 15–25. The comparison with the subgroups observed before debranching shows that a main part of the initial subgroup of DP 25 could be considered as formed with singly branched chains. Furthermore a small proportion of pullulanase resistant ß-limit dextrins was obtained. The obtained results permits one to suggest a new model for the structure of waxy maize amylopectin. On the basis of this model the differences in structure existing between the various starches are discussed and the results are compared with those reported elsewhere for potato starch. A parallelism between crystalline patterns of native starches and the amylopectin structure, particularly its branching degree, is observed.